When one of our SQL Server 2008R2 clusters failed over the amount of time needed between when the server came online and when clients could connect to the instance seemed to be overly long. After some research into the logs I found this error occuring multiple times for different ids, most of the ids were automated processes that connect as quickly as possible.
Login Failed for user 'xxxxx'. Reason: Server is in script upgrade mode. Only administrator can connect at this time.
Going back over the upgrade logs the SQL Instance in question hadn't been patched in quite some time. So what was the reason for the upgrade script running?
I googled for answer and came up empty as to why this would be happening after the patch was successfully installed.
After some additional research the issue was found, SP1 had been installed on the primary node but not the secondary node of the cluster. Each time the instance was failed over the SQL Engine had to perform and upgrade/downgrade of the system databases.
Lesson Learned: Patch one node and schedule the other node upgrade.